/* Get the system load averages.
Copyright (C) 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
Free Software Foundation, Inc.

GNU Make is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3 of the License, or (at your option) any later
version.

GNU Make is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Compile-time symbols that this file uses:

   FIXUP_KERNEL_SYMBOL_ADDR()	Adjust address in returned struct nlist.
   KERNEL_FILE			Pathname of the kernel to nlist.
   LDAV_CVT()			Scale the load average from the kernel.
				Returns a double.
   LDAV_SYMBOL			Name of kernel symbol giving load average.
   LOAD_AVE_TYPE		Type of the load average array in the kernel.
				Must be defined unless
				is defined;
                                or we have libkstat;
				otherwise, no load average is available.
   NLIST_STRUCT			Include nlist.h, not a.out.h, and
				the nlist n_name element is a pointer,
				not an array.
   HAVE_STRUCT_NLIST_N_UN_N_NAME struct nlist has an n_un member, not n_name.
   LINUX_LDAV_FILE		[__linux__]: File containing load averages.

   Specific system predefines this file uses, aside from setting
   default values if not emacs:

   WINDOWS32			No-op for Windows95/NT.
   __linux__			Linux: assumes /proc filesystem mounted.
   				Support from Michael K. Johnson.

   In addition, to avoid nesting many #ifdefs, we internally set
   LDAV_DONE to indicate that the load average has been computed.

   We also #define LDAV_PRIVILEGED if a program will require
   special installation to be able to call getloadavg.  */

/* This should always be first.  */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <sys/types.h>

/* Both the Emacs and non-Emacs sections want this.  Some
   configuration files' definitions for the LOAD_AVE_CVT macro (like
   sparc.h's) use macros like FSCALE, defined here.  */
#if defined (unix) || defined (__unix)
# include <sys/param.h>
#endif


/* Exclude all the code except the test program at the end
   if the system has its own `getloadavg' function.

   The declaration of `errno' is needed by the test program
   as well as the function itself, so it comes first.  */

#include <errno.h>

#ifndef errno
extern int errno;
#endif

#if HAVE_LOCALE_H
# include <locale.h>
#endif
#if !HAVE_SETLOCALE
# define setlocale(Category, Locale)    /* empty */
#endif

#ifndef HAVE_GETLOADAVG


/* The existing Emacs configuration files define a macro called
   LOAD_AVE_CVT, which accepts a value of type LOAD_AVE_TYPE, and
   returns the load average multiplied by 100.  What we actually want
   is a macro called LDAV_CVT, which returns the load average as an
   unmultiplied double.

   For backwards compatibility, we'll define LDAV_CVT in terms of
   LOAD_AVE_CVT, but future machine config files should just define
   LDAV_CVT directly.  */

# if !defined(LDAV_CVT) && defined(LOAD_AVE_CVT)
#  define LDAV_CVT(n) (LOAD_AVE_CVT (n) / 100.0)
# endif

/* Set values that are different from the defaults, which are
   set a little farther down with #ifndef.  */

# if !defined (LDAV_CVT) && defined (FSCALE)
#  define	LDAV_CVT(n) (((double) (n)) / FSCALE)
# endif

# ifdef HAVE_UNISTD_H
#  include <unistd.h>
# endif

# include <stdio.h>

/* LOAD_AVE_TYPE should only get defined if we're going to use the
   nlist method.  */
# if !defined(LOAD_AVE_TYPE) && (defined(LDAV_CVT) || defined(KERNEL_FILE) || defined(LDAV_SYMBOL))
#  define LOAD_AVE_TYPE double
# endif

# ifdef LOAD_AVE_TYPE

#   ifndef __linux__
#    ifdef HAVE_NLIST_H
#     include <nlist.h>
#    else
#     include <a.out.h>
#    endif

#    ifndef KERNEL_FILE
#     define KERNEL_FILE "/vmunix"
#    endif /* KERNEL_FILE */

#    ifndef LDAV_SYMBOL
#     define LDAV_SYMBOL "_avenrun"
#    endif /* LDAV_SYMBOL */
#   endif /* __linux__ */

#  ifndef LDAV_CVT
#   define LDAV_CVT(n) ((double) (n))
#  endif /* !LDAV_CVT */

# endif /* LOAD_AVE_TYPE */

# if defined(HAVE_FCNTL_H) || defined(_POSIX_VERSION)
#  include <fcntl.h>
# else
#  include <sys/file.h>
# endif


#if !defined(HAVE_LIBKSTAT) && defined(LOAD_AVE_TYPE)
/* File descriptor open to /dev/kmem or VMS load ave driver.  */
static int channel;
/* Nonzero iff channel is valid.  */
static int getloadavg_initialized;
/* Offset in kmem to seek to read load average, or 0 means invalid.  */
static long offset;

#if !defined(__linux__)
static struct nlist nl[2];
#endif /* Not linux */

#endif /* LOAD_AVE_TYPE && !HAVE_LIBKSTAT */

/* Put the 1 minute, 5 minute and 15 minute load averages
   into the first NELEM elements of LOADAVG.
   Return the number written (never more than 3, but may be less than NELEM),
   or -1 if an error occurred.  */

int getloadavg(double loadavg[], int nelem)
{
    int elem = 0;               /* Return value.  */

# ifdef NO_GET_LOAD_AVG
#  define LDAV_DONE
    /* Set errno to zero to indicate that there was no particular error;
       this function just can't work at all on this system.  */
    errno = 0;
    elem = -1;
# endif

# if !defined (LDAV_DONE) && defined (HAVE_LIBKSTAT)
/* Use libkstat because we don't have to be root.  */
#  define LDAV_DONE
    kstat_ctl_t *kc;
    kstat_t *ksp;
    kstat_named_t *kn;

    kc = kstat_open();
    if(kc == 0)
        return -1;
    ksp = kstat_lookup(kc, "unix", 0, "system_misc");
    if(ksp == 0)
        return -1;
    if(kstat_read(kc, ksp, 0) == -1)
        return -1;


    kn = kstat_data_lookup(ksp, "avenrun_1min");
    if(kn == 0) {
        /* Return -1 if no load average information is available.  */
        nelem = 0;
        elem = -1;
    }

    if(nelem >= 1)
        loadavg[elem++] = (double) kn->value.ul / FSCALE;

    if(nelem >= 2) {
        kn = kstat_data_lookup(ksp, "avenrun_5min");
        if(kn != 0) {
            loadavg[elem++] = (double) kn->value.ul / FSCALE;

            if(nelem >= 3) {
                kn = kstat_data_lookup(ksp, "avenrun_15min");
                if(kn != 0)
                    loadavg[elem++] = (double) kn->value.ul / FSCALE;
            }
        }
    }

    kstat_close(kc);
# endif /* HAVE_LIBKSTAT */

# if !defined (LDAV_DONE) && defined (__linux__)
#  define LDAV_DONE
#  undef LOAD_AVE_TYPE

#  ifndef LINUX_LDAV_FILE
#   define LINUX_LDAV_FILE "/proc/loadavg"
#  endif

    char ldavgbuf[40];
    double load_ave[3];
    int fd, count;

    fd = open(LINUX_LDAV_FILE, O_RDONLY);
    if(fd == -1)
        return -1;
    count = read(fd, ldavgbuf, 40);
    (void) close(fd);
    if(count <= 0)
        return -1;

    /* The following sscanf must use the C locale.  */
    setlocale(LC_NUMERIC, "C");
    count = sscanf(ldavgbuf, "%lf %lf %lf",
                   &load_ave[0], &load_ave[1], &load_ave[2]);
    setlocale(LC_NUMERIC, "");
    if(count < 1)
        return -1;

    for(elem = 0; elem < nelem && elem < count; elem++)
        loadavg[elem] = load_ave[elem];

    return elem;

# endif /* __linux__ */

# if !defined (LDAV_DONE) && defined (WINDOWS32)
#  define LDAV_DONE

    /* A faithful emulation is going to have to be saved for a rainy day.  */
    for(; elem < nelem; elem++) {
        loadavg[elem] = 0.0;
    }
# endif /* WINDOWS32 */

# if !defined (LDAV_DONE) && defined(LOAD_AVE_TYPE)

    /* UNIX-specific code -- read the average from /dev/kmem.  */

#  define LDAV_PRIVILEGED       /* This code requires special installation.  */

    LOAD_AVE_TYPE load_ave[3];

    /* Get the address of LDAV_SYMBOL.  */
    if(offset == 0) {
#   ifndef NLIST_STRUCT
        strcpy(nl[0].n_name, LDAV_SYMBOL);
        strcpy(nl[1].n_name, "");
#   else /* NLIST_STRUCT */
#    ifdef HAVE_STRUCT_NLIST_N_UN_N_NAME
        nl[0].n_un.n_name = LDAV_SYMBOL;
        nl[1].n_un.n_name = 0;
#    else /* not HAVE_STRUCT_NLIST_N_UN_N_NAME */
        nl[0].n_name = LDAV_SYMBOL;
        nl[1].n_name = 0;
#    endif /* not HAVE_STRUCT_NLIST_N_UN_N_NAME */
#   endif /* NLIST_STRUCT */

        if(
#    if !defined (ps2))
              nlist(KERNEL_FILE, nl)
#    else /* !ps2 */
              knlist(nl, 1, sizeof(nl[0]))
#    endif
              >= 0)
        {
#    ifdef FIXUP_KERNEL_SYMBOL_ADDR
            FIXUP_KERNEL_SYMBOL_ADDR(nl);
#    endif
            offset = nl[0].n_value;
        }
    }

    /* Make sure we have /dev/kmem open.  */
    if(!getloadavg_initialized) {
        channel = open("/dev/kmem", 0);
        if(channel >= 0) {
            /* Set the channel to close on exec, so it does not
               litter any child's descriptor table.  */
#   ifdef F_SETFD
#    ifndef FD_CLOEXEC
#     define FD_CLOEXEC 1
#    endif
            (void) fcntl(channel, F_SETFD, FD_CLOEXEC);
#   endif
            getloadavg_initialized = 1;
        }
    }

    /* If we can, get the load average values.  */
    if(offset && getloadavg_initialized) {
        /* Try to read the load.  */
        if(lseek(channel, offset, 0) == -1L
           || read(channel, (char *) load_ave, sizeof(load_ave))
           != sizeof(load_ave)) {
            close(channel);
            getloadavg_initialized = 0;
        }
    }

    if(offset == 0 || !getloadavg_initialized)
        return -1;
# endif /* LOAD_AVE_TYPE */

# if !defined (LDAV_DONE) && defined (LOAD_AVE_TYPE)    /* Including VMS.  */
    if(nelem > 0)
        loadavg[elem++] = LDAV_CVT(load_ave[0]);
    if(nelem > 1)
        loadavg[elem++] = LDAV_CVT(load_ave[1]);
    if(nelem > 2)
        loadavg[elem++] = LDAV_CVT(load_ave[2]);

#  define LDAV_DONE
# endif /* !LDAV_DONE && LOAD_AVE_TYPE */

# ifdef LDAV_DONE
    return elem;
# else
    /* Set errno to zero to indicate that there was no particular error;
       this function just can't work at all on this system.  */
    errno = 0;
    return -1;
# endif
}

#endif /* ! HAVE_GETLOADAVG */

#ifdef TEST
#include "make.h"

int main(int argc, char **argv)
{
    int naptime = 0;

    if(argc > 1)
        naptime = atoi(argv[1]);

    while(1) {
        double avg[3];
        int loads;

        errno = 0;              /* Don't be misled if it doesn't set errno.  */
        loads = getloadavg(avg, 3);
        if(loads == -1) {
            perror("Error getting load average");
            exit(1);
        }
        if(loads > 0)
            printf("1-minute: %f  ", avg[0]);
        if(loads > 1)
            printf("5-minute: %f  ", avg[1]);
        if(loads > 2)
            printf("15-minute: %f  ", avg[2]);
        if(loads > 0)
            putchar('\n');

        if(naptime == 0)
            break;
        sleep(naptime);
    }

    exit(0);
}
#endif /* TEST */
